Method of selecting and/or processing wood according to fibre characteristics

ABSTRACT

The invention provides a method for predictively assessing one or more characteristics of wood pulp produced from solid wood. The method comprises the steps of determining the velocity of sound through the solid wood, and assessing characteristic(s) of wood fiber or wood pulp produced from the wood by reference to the velocity of sound through the solid wood. The method may also comprise the steps of causing a sound wave to be transmitted through the wood, determining the velocity of the sound wave through the wood, and comparing the result to stored information on fiber characteristic(s) versus sound velocity through the wood-type to determine the fiber characteristic(s) for the wood.

FIELD OF INVENTION

The invention comprises a method for predictively assessing one or morecharacteristics of wood fibre or wood pulp produced from wood while thewood is in solid form, such as fibre length or the strength of pulpformed from the wood. The invention has particular application in theselection of wood for pulp and paper or other wood-fibre-basedapplications such as the production of fibre board.

BACKGROUND OF INVENTION

Optimum segregation of tree stems after felling, or of logs after sawingof the stems into logs, for different applications such as solid orstructural grade lumber, manufacture of reconstituted wood products, orpulp and paper manufacture, is an important issue for the forestry andwood products industries because of the variable nature of the rawmaterial and the different properties required in different endproducts. There are major commercial benefits to be gained by optimisingthe use of the wood resource for different solid wood, reconstituted,and pulp and paper applications, which may require different propertiesin the raw material. Differences in the raw material arise due togenetic differences, silvicultural differences, and geographical andsite differences. Even within a tree there are differences in woodproperties between the corewood of the tree and the outer wood, and alsovariations from the bottom to the top of the tree, which furthercomplicates the wood segregation issue.

At present, historical wood density information and a general knowledgeof trends in fibre properties in different parts of the tree are theonly tools available to perform some limited segregation of wood forpulp and paper manufacture for example. Basic density is difficult tomeasure, and it is correlated with fibre properties only at a populationlevel and so cannot be applied at an individual tree or log level.Little information on wood quality at an individual stand level isavailable, other than average wood density data from historicalmeasurements, and there is generally no information at all at anindividual tree level. To date, basic wood density is the only toolavailable. Most wood properties are related to the basic density of thewood (ie the amount of dry wood substance per unit volume of wood), butbasic density is difficult to measure and impossible to usefully applyat a whole tree level. Density is also a measure of the amount of woodsubstance and void space in a unit volume of wood, and is not indicativeof the number of fibres which make up that space. For example,individual trees can have roughly the same chip basic density, but havevery different fibre lengths, fibre width and thickness, fibre wallareas (coarseness), and number of fibres per unit mass of wood.

Some wood segregation on the basis of density is practised in pulp andpaper manufacture. High density wood from the outside of the tree (theslabwood) generally has long and coarse (thicker-walled) fibres whichare suitable for certain products such as cement-board reinforcing pulpand sack grades. Wood from the top of the tree is more like corewood andhas lower density with shorter, thinner walled (low coarseness) fibres.Pulp from this wood is more suitable for printing and writing or tissuegrade papers for example. However basic density is still a very crudebasis for wood segregation and knowledge of density variability israther poor.

Softwood kraft pulp qualities are normally determined by the handsheetproperties of apparent density or bulk, tensile strength, andout-of-plane tear strength. Fibre length is the critical softwood kraftpulp fibre determinant. With too little fibre length such pulps losetheir characteristic softwood reinforcement properties. However, verylong, coarse fibres can be difficult to refine and are prone toflocculation and sheet formation becomes a problem. Other fibreproperties are also important but only after fibre length requirementsare met. Fibre length is critical for the reinforcement properties ofsoftwood kraft pulps. If pulp fibre length falls below a certaincritical level of about 2.0-2.1 mm, bulk is abruptly decreased andreinforcement tear/tensile strengths are correspondingly, abruptlylowered.

The Wet Zero Span Tensile (WZST) strength of a pulp is influenced by thenumber of fibres per unit mass of pulp and by the strength of theindividual fibres. Individual fibre strength is in turn influenced byfibre coarseness and intra-fibrewall characteristics such asmicro-fibril angle (MFA). WZST strength is a good predictor of TearIndex at a given Tensile Index, the traditional indicator of softwoodkraft reinforcement potential.

Pulp quality is very much a function of its end-use. As well as theabove mentioned quality factors, end-users of market pulps are alsoconcerned about: ease of beating the amount of energy required to refinea pulp to an acceptable tensile strength; reinforcement potential; andeffects on paper sheet formation.

Pulp and paper mills normally utilise the residues from harvesting suchas top logs and low grade logs that arise during harvesting operations,and from saw milling such as chips from the slabwood sawn from theoutsides of the log.

The measurement of velocity of sound in a log is a non-destructivetechnique which can be used to evaluate the stiffness of materials bymeans of sound transmission. The sound wave, for instance induced by theimpact of a hammer at one end, travels down the length of a log. Thetransit time (Δt) is measured. The modulus of elasticity (MOE) iscomputed from the transit time and density (p) as follows:

MOE=V ² p=(l/Δt)² p

This is a fundamental relationship for materials. Although a log of woodis not a homogeneous material (compared with an iron bar, for example),and does not obey this law perfectly, relatively good relationships havebeen found between sound wave speed and the average measured stiffnessof lumber which is sawn from the log. U.S. Pat. No. 4,144,669 describesthe use of velocity of sound measurement for the grading of wood.Measurements of velocity of sound in a log can be made with industrialstress wave timers, which are commercially available.

SUMMARY OF INVENTION

In broad terms in one aspect the invention comprises a method forpredictively assessing one or more characteristics of wood fibre or woodpulp produced from solid wood, comprising determining the velocity ofsound through the solid wood, and assessing characteristic(s) of woodfibre or wood pulp produced from the wood by reference to the velocityof sound through the solid wood.

More particularly the method comprises causing a sound wave to betransmitted through the wood, determining the velocity of the sound wavethrough the wood, and comparing the result to stored information onfibre characteristic(s) versus sound velocity through the wood-type todetermine the fibre characteristic(s) for the wood.

In one form the method includes placing a sensing means capable ofdetecting sound in the wood in contact with or within sensing distanceof one end of the length of wood, placing a second sensing means capableof detecting sound in the wood in contact with or within sensingdistance of another end of the length of wood, causing a sound wave tobe transmitted in the length of wood from one end to the other,detecting the sound at each end of the log or length of wood,determining the velocity of the sound in the wood, and assessingcharacteristic(s) of wood fibre or wood pulp produced from the wood byreference to stored information on fibre characteristics versus soundvelocity through the wood.

In another form the method includes placing means capable of detectingboth an original and reflected sound wave in contact with or withinsensing distance of one end of the length of wood, causing a sound waveto be transmitted in the length of wood, detecting a reflected echo ofthe sound in the wood, determining the velocity of the sound in thewood, and assessing characteristics of wood fibre or wood pulp producedfrom the wood by reference to stored information on fibrecharacteristics versus sound velocity through the wood.

In broad terms in another aspect the invention comprises apparatus forpredictively assessing one or more characteristics of wood fibre or woodpulp produced from solid wood, comprising sensing means capable ofdetecting the velocity of sound in through the wood, and computerprocessing means comprising stored information on fibre characteristicsversus sound velocity in wood and arranged to determine the fibrecharacteristic(s) by reference to said stored information on fibrecharacteristic(s) versus velocity through the wood.

By “sound” is meant normally relatively low frequency energy that willbe audible to the human ear eg of the order of 500 to 1000 Hz as will becreated by a single impact on a length of wood, by striking the lengthof wood with a hammer for example. Higher frequencies may be used suchas of the order of 15 kHz or above including ultrasound but use of lowerfrequencies is preferred.

The method and apparatus of the invention may be used with whole stemsafter felling, logs and sawing of the stems into logs, flitches, cents,or other lengths of lumber or wood in any form, and in thisspecification and claims “length of wood” is to be understoodaccordingly.

BRIEF DESCRIPTION OF THE FIGURES

The invention is further described with reference to the accompanyingfigures in which:

FIG. 1 is a schematic representation of the source of material for apulp mill;

FIG. 2 is a schematic representation of potential commercial applicationof the method of the invention at a pulp mill,

FIG. 3 is a graph of average length weighted average fibre length (LWFL)against sound speed results from the trial described in example 1,

FIG. 4 is a graph of Wet Zero Span Tensile (WZST strength) versus soundspeed results from the trial described in example 1,

FIG. 5 is a graph of WZST strength versus average log group sound speedresults from the trial described in example 2,

FIG. 6 is a graph of LWFL versus average log group sound speed resultsfrom the trial described in example 2,

FIG. 7 is a graph of handsheet bulk versus average log group sound speedmeasurement results from the trial described in example 2,

FIG. 8 is a graph of handsheet Tensile and Tear Indices versus averagelog group sound speed measurement results from the trial described inexample 2,

FIG. 9 is a graph of average pulp fibre length versus log sound speedfor log type results from the trial described in example 3, and

FIG. 10 is a graph of pulp (WZST) strength versus log sound speed by logtype results from the trial described in example 3.

DETAILED DESCRIPTION OF INVENTION

As stated we have found a close correlation between the velocity rate ofsound, preferably relatively low frequency sound, through wood and thefibre characteristics of the wood on subsequent fiberising of the wood,in particular the fibre length, and properties of pulp produced usingthe wood which are dependent on the fibre characteristics of the wood.

In the method of the invention, wood fibre or wood pulp characteristicsfor wood whole stems, logs, or in other form are predictively assessedby reference to the velocity of sound through the wood. The methodinvolves causing a sound wave to be transmitted through the wood, forexample by impacting the wood such as by striking the wood, determiningthe velocity of sound through the wood, and comparing the result tostored information on fibre characteristics versus sound velocitythrough the wood-type or species to derive information predictive of thecharacteristics of wood fibre or pulp produced from the wood. Any deviceable to determine the velocity of sound including low frequency sound oralternatively higher frequency sound through the wood may be used tomeasure the time taken for the sound wave to be transmitted through thelength of wood from one end to the other. Sound in the wood may becreated by impacting the wood with a hammer for example, or byelectronic means. The device may comprise one or more sensing headswhich contact the wood or are positioned within sensing distance of thewood, such as one or more small microphones spaced from the wood by afoam pad for example. The device may comprise one sensing head at thesend end of the length of wood and another at the other (receive) end ofthe length of wood to sense the time taken for the sound to betransmitted over the length of wood, or a single sensing head at one endof the length of wood which senses the time taken for the sound to betransmitted over the length of wood and reflected back to the same endof the length of wood. The output is fed to computer processing meanscomprising in memory stored information on fibre characteristics versusvelocity of sound through the wood-type or species, and a measure of thefibre or pulp characteristics determined, which may be output as adisplay on a hand held device, to a memory storage device such as afloppy disc, or to a control system controlling, sorting, chipping,sawing of logs or similar.

FIG. 1 is a schematic representation of the source of primary materialfor a pulp and paper mill. Logs may be assessed as they are received ata pulp and paper mill prior to processing. Alternatively, loggingcompanies may assess whole logs to select whole logs and/or slabwood inthe form of sawmill wood chips for subsequent pulping. Results of thedata recorded for each log may then be used to determine approximateexpected average pulp fibre length and pulp strength characteristics forpulp if formed from that log or slabwood portion of the log bycomparison of the data with correlations for velocity of sound withaverage pulp fibre length or pulp strength.

Logs having velocity of sound characteristics within specified rangesmay be identified by an identification means so that each log or theslabwood arising from a sawn log is allocated to a batch for use in themanufacture of a particular pulped product. For example, wood producingpulp having a shorter length weighted average fibre length (LWFL) and alower WZST strength is preferred for use in the manufacture of very highdensity papers such as release papers and glassine. High LWFL and WZSTstrength pulp is most appropriately used for very high tearing strengthgrades of paper, such as fibre-cement grades. Table 1 shows preferredend-use applications for radiata pine wood producing kraft pulp havingspecified fibre-length/pulp properties.

TABLE 1 Radiata Pine Kraft Pulp Properties versus End-Use ApplicationsAverage Coarse- Fibres/g o.d. WZST LWFL ness pulp Strength RefiningEnd-use (mm) (mg/m) (relative) (km Response (examples) 1.80-2.00 0.16100  10-11 Beats easily to form high Very high density papers e.g.density sheets of relative low release papers and glassine tensilestrength 2.00-2.20 0.18 86 11-12 Beats easily to form sheets of Good forreinforcement in high density with moderate products requiring lowtensile strength coarseness fibres, for example in some tissue grades2.20-2.40 0.20 69 12-14 Moderately easy to beat Excellent forreinforcement forming sheets of intermediate component of printing anddensity with good tensile writing grades (fine papers) strength2.40-2.60 0.23 54 14-16 Medium - high coarseness Suitable formanufacture of fibres with good tearing products which value highstrengths; slower beating tearing strength, such as response somepackaging grades >2.60 0.26 44 16-17 Long, coarse fibres that are Veryhigh tearing strength difficult to refine forming suitable for somespeciality bulky sheets grades, such as for fibre- cement boardmanufacture, and for papers of high bulk

FIG. 2 further illustrates potential commercial application of themethod of the invention for pulp log sorting. Acoustic wave testing ofwhole stems or logs can occur both at the log landing adjacent toharvesting operations and at central log handling facilities, such asthe log yard of a pulp mill. Testing at log landings has the advantagethat both saw logs and pulp logs can be characterised by sound speedbefore decisions are made as to which processing facility they are sentto. For example, the sound speed measurement can be used to select sawlogs of superior stiffness for sawing into structural grade lumber.However, testing at the log landing will most likely be a manualoperation using hand-held devices so may be rather labour intensive.

Pulp logs X which have already been tested for sound speed at the loglanding, on arrival at the pulp mill log yard, can be immediatelyallocated to a particular log pile A, B, C based on this characteristic.Nevertheless, it may be preferable for some processing operations tohave automated sound speed measurement at a central stem or log handlingfacility. The pulp mill log yard would be one such facility in whichlarge numbers of logs can be tested and segregated into different logpiles according to sound speed.

All logs arriving at the central log handling facility can be receivedon a landing which automatically conveys them into a stress wave testingcentre 10. Automatic acoustic testing could involve equipment whichcould grip each log, measure its length, sense the position of one orboth log ends, and then automatically apply the acoustic wave transittime measurement. The log would then be “bucked” off the main chainconveyor 11 onto one of several decks 12 according to the measuredvelocity of sound. Logs with speeds within given ranges would beclassified according to the pulp mill's product requirements. Logstackers would then move the logs from each landing into separate logpiles A, B, C, each representing a separate sound speed class.

The logs would then be processed in chippers 13, 14. Chipping operationsat pulp mills can typically feed chips into several different chip piles15, 16, 17 18. Chips are then reclaimed off these piles and fed into thevarious pulp mill processing lines 19, 20, 21. Different pulping linesmay be dedicated to different product types or a pulping line may swingbetween different pulp grades using a campaigning strategy.

In either case, chips can normally be fed into a pulping line from anyof the different chip piles.

Pulp mills also receive a large amount of their wood supply in the formof wood chips Z, which are produced at saw mills from the waste slabwoodtaken from the outside of saw logs. If a saw log has been tested forsound speed before sawing, such that logs of a given sound speed classcan be sawn as a batch, then the chips arising from the slabwood wouldalready be characterised as to their end-use suitability for processinginto pulp. On arrival at the pulp null, such “sound-speed characterised”saw mill chips 22 could be blended into the appropriate chip pile 15,16, 17, 18.

It will be appreciated that FIG. 2 is simply one example of a possiblepulp log sorting process involving the method of the present invention,and other examples might include any number of categories of logs,chippers, chip pile categories and pulp line.

The method of the invention may be used to select wood for theproduction of kraft pulp, for other types of pulping such assemi-chemical, chemical, chemi-mechanical, and mechanical pulping, andalso for use in the selection of wood for other wood-fibre-basedapplications such as fibre board production including the production ofmedium density fibre board in particular.

The method of the invention is further illustrated by the followingexamples:

EXAMPLE 1

250 logs of radiata pine taken randomly from a lumber mill were peeledto expose the corewood at the centre of the log. Each peeler core wastested for speed of sound (using a Metriguard Model 239A stress wavetimer), before samples from each log were taken for subsequentmeasurement of key pulp and paper properties.

The peeler cores, and their corresponding discs removed for pulping,were divided into classes with respect to sound speed. The sound speedsvaried from 1.44 to 4.16×10³ m/s, and the population of peeler cores wasdivided into classes at 0.157×10³ m/s intervals, giving a total of 18sound classes, each containing between 2 and 34 peeler core samples.

The samples for each sound speed class were grouped, chipped and pulped.The half scale Kappa number of each pulp was tested to ensure that ithad been delignified sufficiently, and if so handsheets were formed formeasurement of WZST strength, internal tearing resistance and tensilestrength characteristics. In addition fibre length measurements weretaken using a Kajaani FS200 fibre analyser. Length weighted averagefibre length (LWFL) and weight weighted average fibre length (WWFL) werecalculated.

The average velocity of sound and the number of peeler cores in eachclass are shown in Table 2. The distribution for the 18 sound classeswas within sensing distance of normal.

Large variations in both average fibre length and pulp strength wereobserved across the 18 sound classes of wood. This was an unexpected andsurprising result given that the sample population of 250 samples allcontained only corewood. The average fibre length ranged from 1.77 to2.78 mm LWFL, whilst the average pulp strength ranged from 9.92 to 16.54km WZST.

A strong correlation was identified between sound speed and fibre length(R² of 89%) and sound speed vs WZST strength (R² of 93%) as shown inFIGS. 3 and 4 which show LWFL versus sound speed for each of the 18sound classes and WZST breaking length versus average sound speed foreach of the 18 sound classes, respectively.

The strong correlation between average LWFL and sound speed isremarkable, as is the distinct difference between the fibre lengthdistributions for the different sound classes. For example, thedistribution for class 16 (from 3.7 to less than 3.86×10³ m/s) wouldnormally be associated with high density slabwood chips and notcorewood. In contrast classes 1 and 2 (1.35 to less than 1.66×10³ m/s)contained very short fibres, even shorter than would normally beassociated with corewood. Previously available information, based onbasic density information, had indicated that corewood samples of thetype employed in this trial should have been reasonably homogeneous inrelation to fibre quality. These results clearly show this not to be thecase. Similarly, with regard to WZST strengths, strengths greater than15 km are normally associated with high density, slabwood chips whereassome of the core samples had WZST strengths as high as 16.5 km.

TABLE 2 Sound Class Data Class Average Number Limits Velocity ofCumulative (×10³ m/s) (×10³ m/s) Cores Percentage 1.35-1.50 1.44  2 0.81.50-1.66 1.60  2 1.6 1.66-1.82 1.75 12 6.4 1.82-1.97 1.89 16 12.81.97-2.13 2.11 15 18.8 2.13-2.29 2.20 24 28.4 2.29-2.44 2.35 22 37.22.44-2.60 2.50 29 48.8 2.60-2.76 2.68 34 62.4 2.76-2.92 2.81 21 70.82.92-3.07 2.98 23 80.0 3.07-3.23 3.13 10 84.0 3.23-3.39 3.24 15 90.03.39-3.54 3.45 10 94.0 3.54-3.70 3.59  5 96.0 3.70-3.86 3.74  4 97.63.86-4.01 3.96  4 99.2 4.01-4.17 4.16  2 100

Example 2

250 logs of 12-42 cm large end diameter were tested for sound speedtransmission (using Metriguard Model 239A stress wave timer). The logswere segregated into one of four groups based on sound speed:

Group 1: velocity<2.72 km/s

Group 2: 2.72≦velocity<3.07 km/s

Group 3: 3.07≦velocity<3.40 km/s

Group 4: velocity≧3.40

The logs in each group were then chipped with a composite samplecollected as the chips exited the chipping plant, so that four compositesamples were collected, representative of the chips generated from eachsound speed group.

Each chip sample was screened to remove oversized chips and fines andthen kraft pulped under standard conditions (16% Effective Alkali, 30%Sulphidity, 1 hour time-to-temperature, 1 hour at 170° C.) toapproximately 26 kappa number. The pulps were washed and screened toremove shives, and then evaluated for properties.

LWFL was measured with a Kajaani FS200 fibre analyser. Pulps wererefined in the PFI Mill for 1000 revolutions and standard handsheetsprepared according to appropriate Appita standard methods. WZST strengthwas measured with a Pulmac TS100 Tensile Tester and other handsheetproperties were measured according to Appita standards. The basicdensity of the chips was also measured according to the Appita standard.

The characteristics of the four sound classes are shown in Table 3.

TABLE 3 Characteristics of four sound classes Wood Chip PropertiesHandsheet Properties at 1000 Average Pulp PFI Revolutions Basic GroupProperties Tensile % Dry Density Velocity WZST LWFL Bulk Index TearIndex Group Content (kg/m³) (km/s) (km) (mm) (cm³/g) (Nm/g) (mNm²/g) 137.8 374 2.63 15.80 2.62 1.31 85.92 11.10 2 39.6 379 2.91 16.07 2.601.35 84.14 11.56 3 41.7 389 3.20 17.17 2.78 1.37 80.43 13.67 4 46.3 4283.49 17.64 2.87 1.44 78.27 16.86

The relationship between pulp properties and average class sound speedare shown in FIGS. 5 to 8, which show respectively the WZST strength,LWFL, handsheet bulk, and handsheet Tensile and Tear Indices versusaverage log group sound speed measurement for the four sound classes.

It is evident from the data that the pulps generated from the four loggroups are distinctly different in properties. Hence, segregation of thelogs has resulted in a useful classification according to their fibreproperties. Surprisingly, log groups 1-3 have relatively low basicdensity, yet relatively high fibre lengths and pulp strengths. Thisfurther indicates the superior predictive ability of sound speed overbasic density as an indicator of fibre properties.

Example 3

Eighty trees were felled from a 27 year old radiata pine plantation onthe Mamaku Plateau in the Central North Island of New Zealand. Each stemwas cut into four logs of 4.2 m length, yielding approximately 300 logswhich were then tested for sound speed transmission using MetriguardModel 239A Stress Wave Timer. The logs were segregated into four groupsaccording to their position within the stem. The range of sound speedswithin each group were normally distributed with means and ranges asfollows:

Mean velocity (km/s) Range (km/s) Butt 2.55 1.98-3.21 Second 2.812.22-3.73 Third 2.78 2.29-3.63 Top 2.69 2.21-3.34

Within each log group, four sets of 5 logs were selected—the slowest 5logs, 5 logs at the 33^(rd) percentile of speed, 5 logs at the 66^(th)percentile of speed, and the 5 fastest logs (the sub groups weredesignated I-IV respectively). Thus 20 individual logs were selected foreach log group (Butt, Second, Third, and Top) giving 80 logs in total.

The logs were then cant-sawn into lumber according to a standardpattern, with the identification of each log tracked through thesawmill. The outerwood slabs from each log were passed through a chipperand a composite chip sample was collected.

The chip samples were combined into a single composite sample for eachsub-group of 5 logs (I, II, III and IV) for each log type (Butt, Second,Third, and Top). Thus, 16 composite chip samples were obtained, 4 foreach log type.

Each chip sample was screened to remove oversized chips and fines andthen kraft pulped under standard conditions (16% Effective Alkali, 30%Sulphidity, 1 hour time-to-temperature, 1 hour at 170° C.) toapproximately 26 kappa number. The pulps were washed and screened toremove shives, and then evaluated for properties.

LWFL was measured with a Kajaani FS200 fibre analyser. Pulps wererefined in the PFI Mill for 1000 revolutions and standard handsheetsprepared according to appropriate Appita standard methods. WZST strengthwas measured with a Pulmac TS100 Tensile Tester.

The average sound speed of each log group is shown in Table 4 along withthe properties of the pulps derived from the outerwood chip samples.

TABLE 4 Log class sound speeds and the properties of the derived pulpsSample Average Sound Fibre Length WZST Strength ID Speed (km/s) (LWFL,mm) (km) Butt Logs Group I 2.08 2.72 15.40 Group II 2.45 2.90 16.76Group III 2.65 2.72 16.60 Group IV 3.06 2.82 17.52 Second Logs Group I2.28 2.80 16.01 Group II 2.69 2.93 16.85 Group III 2.93 3.00 18.13 GroupIV 3.39 3.10 19.03 Third Logs Group I 2.34 2.66 15.91 Group II 2.69 2.9317.33 Group III 2.85 2.83 17.68 Group IV 3.35 3.09 18.59 Top Logs GroupI 2.29 2.49 14.19 Group II 2.61 2.78 17.02 Group III 2.79 2.65 17.57Group IV 3.13 2.94 18.57

FIGS. 9 and 10 respectively plot LWFL and WZST strength against averagelog group sound speed.

All the WZST strength data fall on the same trend line with sound speed,regardless of log position in the tree. This is a useful observation,since outerwood from sawmills could be segregated for pulp processing(based on expected pulp strength) on the basis of the whole log soundspeed. This would only require the sawmill to saw logs in batches basedon sound speed, so that outerwood chips could be convenientlysegregated.

The foregoing demonstrates that for radiata pine pulp wood of varyingquality the method of the invention may closely determine fibreproperties of pulps including fibre length, pulp strength, and paperproperties. It is well known that pulp and paper properties relate tofibre dimensions for pulps from hardwood species such as eucalyptus.

The foregoing describes the invention including preferred forms thereof.Alterations and modifications as will be obvious to those skilled in theart are intended to be incorporated within the scope hereof.

What is claimed is:
 1. Apparatus for predictively assessing a measure of the average fibre length of wood fibre or wood pulp to be produced from a solid wood member, comprising: a sensor capable of detecting the velocity of a sound wave through a solid wood member along the length thereof; and a computer comprising stored information on fibre length of produced wood fibre or wood pulp versus sound velocity through wood and arranged to determine a measure of average fibre length for the wood fibre or wood pulp to be determined by reference to said stored information on fibre length versus detected velocity through the solid wood member.
 2. Apparatus for predictively assessing a measure of average fibre length of wood fibre or wood pulp to be produced from a solid wood member, comprising: a sensor capable of detecting both an original and a reflected sound wave in a solid wood member along the length thereof; and a computer comprising stored information on fibre length of produced wood fibre or wood pulp versus sound velocity through wood and arranged to determine a measure of average fibre length for the wood fibre or wood pulp to be produced by reference to said stored information on fibre length versus detected velocity through the solid wood member.
 3. Apparatus according to claim 1 arranged to determine a measure of strength of pulp to be produced from a solid wood member.
 4. Apparatus for predictively assessing at least one characteristic of wood fibre or wood pulp to be produced from a solid wood member, wherein the characteristic is average fibre length, comprising: a sensor capable of detecting both an original and a reflected sound wave in a solid wood member along the length thereof; and a computer comprising stored information on fibre characteristics versus sound velocity through wood and arranged to determine a measure of the average fibre length of wood fibre to be produced from the solid wood member by reference to said stored information on the average fibre length versus detected sound velocity through the solid wood member. 